Rotating damper

ABSTRACT

A cam member  5  is disposed within a first chamber R 1  such that the cam member  5  is rotatable but non-movable in the axial direction. The cam member  5  is non-rotatably connected to a rotor  3  through a connection shaft portion  52  piercing into a piston  4.  A second cam mechanism  10  is disposed between the cam member  5  and the piston  4.  When the cam mechanism  7  causes the piston  4  to move from the second chamber R 2  side to the first chamber R 1  side in accordance with rotation of the rotor  3  in one direction, the second cam mechanism  10  allows the piston  4  to move from the second chamber R 2  side to the first chamber R 1  side by the same amount of movement. When the second cam mechanism  10  causes the piston  4  to move from the first chamber R 1  side to the second chamber R 2  side in accordance with rotation of the rotor  3  in the other direction, the cam mechanism  7  allows the piston  4  to move from the first chamber R 1  side to the second chamber R 2  side by the same amount of movement.

TECHNICAL FIELD

This invention relates to a rotary damper which is disposed between adevice main body and a rotary member rotatably supported on the devicemain body such as a main body of a toilet and its cover and adapted toprevent high-peed rotation of the rotary member in at least onedirection, thereby rotating the rotary member at a reduced speed.

BACKGROUND ART

As a conventional rotary damper of this type, there is one, for example,which is disclosed in Japanese Patent Application Laid-Open No.H10-311359. This rotary damper includes a cylindrical casing having aclosed bottom portion, a rotor fitted to an open side end portion of thecasing such that the rotor is rotatable but non-movable in the axialdirection, a piston disposed between the rotor and the bottom portionwithin the casing such that the piston is movable in the axial directionbut non-rotatable, and a coiled spring (biasing means) for urging thepiston against the rotor. The mating surfaces of the piston and rotorare each provided with a cam surface. Owing to this cam surface, whenthe rotor is rotated in one direction, the piston is moved from thesecond chamber side to the first chamber side. When the rotor is rotatedin the other direction, the piston is moved from the first chamber sideto the second chamber side by the coiled spring. Between the firstchamber and the second chamber, there are defined a communication pathcapable of flowing a viscous fluid filled in each chamber almost withoutany resistance and an orifice (resistance path) capable of flowing theviscous fluid with a large resistance. The communication path isprovided with a stop valve for opening/closing the path. This stop valveis arranged such that the valve is opened when the viscous fluid in thefirst chamber is flowed into the second chamber and the valve is closedwhen the fluid is flowed from the second chamber into the first chamber,for example.

In the rotary damper thus construction, when the piston is moved fromthe second chamber side to the first chamber side by the rotor which isrotated in one direction, the viscous fluid in the first chamber isgoing to flow into the second chamber. However, since the stop valvecloses the communication path at that time, the viscous fluid in thefirst chamber is flowed into the second chamber through the orifice. Asa result, high speed movement of the piston towards the first chamberside is prohibited, and hence, high speed rotation of the rotor isprohibited. On the contrary, when the piston is moved from the firstchamber side to the second chamber side by the rotor which is rotated inthe other direction, the viscous fluid in the second chamber is flowedinto the first chamber. Since the stop valve opens the communicationpath at that time, the viscous fluid in the second chamber is flowedinto the first chamber through the communication path almost without anyresistance. Thus, the rotor can rotate at a high speed.

In case the conventional rotary damper is used in a toilet, a casing isnon-rotatably connected to a toilet main body and the rotor isnon-rotatably connected to a toilet cover, for example. In this case,the direction of rotation where high speed rotation of the rotor isprohibited is brought into alignment with the direction of closingrotation of the toilet cover. By installing the rotary damper in thisway, when the toilet cover is to be closed, speed of rotation of thetoilet cover is retrained to a low speed so that the toilet cover isprevented from hitting the toilet main body at a high speed, and whenthe toilet cover is to be opened, the cover can be rotated at a highspeed.

When the rotor is rotated in the other direction (direction of rotationwhere high speed rotation is allowed), the piston is moved from thefirst chamber side to the second chamber side by the biasing force ofthe coiled spring. At that time, if the rotor is rotating at a lowspeed, the piston is moved to the second chamber side while maintaininga contacting state of the rotor against the cam surface. However, incase the rotor is rotated at a high speed in the other direction, highspeed movement of the piston is prohibited by viscous resistance of theviscous fluid existing between an inner peripheral surface of thecylinder and an outer peripheral surface of the piston. As a result, thepiston is occasionally spaced apart from the cam surface of the rotornevertheless the piston is biased towards the rotor side by the coiledspring. When the rotor is rotated in one direction with the pistonspaced apart from the rotor, the rotor can rotate without any resistanceuntil the cam surface of the rotor comes into contact with the piston.For this reason, if a hand should be spaced apart from the toilet coverduring the time the toilet cover is rotating in the opening direction ata high speed, for example, the toilet cover would be rotated in theclosing direction at a high speed with such an inconvenient result thatthe toilet cover hits the toilet main body.

DISCLOSURE OF INVENTION

The present invention has been accomplished in order to solve theabove-mentioned problem. The feature of the present invention resides ina rotary damper including a casing having a receiving hole, a rotorfitted to the receiving hole such that the rotor is non-movable in anaxial direction thereof but rotatable, a piston inserted into thereceiving hole between the rotor and a bottom portion of the receivinghole such that the piston is movable in the axial direction thereof butnon-rotatable, and for defining the inside of the receiving hole into afirst chamber on the bottom portion side and a second chamber on therotor side, and viscous fluid filled in the first and second chambers, acam mechanism for allowing movement of the piston from the secondchamber side to the first chamber side when the rotor is rotated in onedirection and for allowing movement from the first chamber side to thesecond chamber side when the rotor is rotated in the other directionbeing disposed between the rotor and the piston, wherein a cam member isdisposed within the first chamber such that the cam member isnon-movable in the axial direction of the receiving hole but rotatable,the cam member is non-rotatably connected to the rotor, a second cammechanism for allowing movement of the piston from the second chamberside to the first chamber side by the cam mechanism when the rotor isrotated in one direction and for allowing movement of the piston fromthe first chamber side to the second chamber side when the rotor isrotated in the other direction is disposed between the rotor and thepiston, and amounts of movement of the piston corresponding to rotationof the rotor by the second cam mechanism and the cam mechanism are setto be equal.

In this case, it is preferred that there are provided a communicationpath for flowing the viscous fluid without any resistance and aresistance path for flowing the viscous fluid with a predetermined valueof resistance, between the first chamber and the second chamber, and astop valve for opening the communication path when the viscous fluidflows in one direction within the communication path and for closing thecommunication path when the viscous fluid flows in the other directionwithin the communication path is disposed at the communication path. Itis also preferred that the piston has a through hole formed in a centralarea thereof and extending in an axial direction thereof, and the rotorand the cam member are non-rotatably connected to each other through aconnection shaft rotatably inserted into the through hole.

It is preferred that an adjustment member for adjusting a flow path areaof the resistance path is disposed at the resistance path such that theadjustment member can be operated from outside. It is also preferredthat the piston has a through hole formed in a central area thereof andextending therethrough in an axial direction thereof, and the rotor andthe cam member are non-rotatably connected to each other through aconnection shaft rotatably inserted into the through hole. It is alsopreferred that the resistance path includes a first hole extendingthrough a central area of the cam member in an axial direction thereof,a second hole extending through a central area of the connection shaftin an axial direction thereof, and a lateral hole extending from thesecond hole to an outer peripheral surface of the connection shaftfacing the second chamber, an insertion hole is formed in a central areaof the rotor in such a manner as to extend therethrough in an axialdirection thereof, and the adjustment member is inserted at least intothe second hole from an external opening portion of the insertion hole.

It is preferred that the rotary damper further comprises inlet pathscommunicating with the first chamber or the second chamber from outside,and wherein the inlet paths are provided, in the form of a seal, with anamount adjusting member, whose insertion amount into the inlet paths canbe operated from outside. It is also preferred that the piston has athrough hole formed in a central area thereof and extending therethroughin an axial direction thereof, and the rotor and the cam member arenon-rotatably connected to each other through a connection shaftrotatably inserted into the through hole. It is also preferred that theinlet paths includes a first hole extending through a central area ofthe cam member in an axial direction thereof, a second hole extendingthrough a central area of the connection shaft in an axial directionthereof, and an insertion hole extending through a central area of therotor in an axial direction thereof, and the amount adjusting member isinserted into the inlet path from an external opening portion of theinsertion hole.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view showing a first embodiment of the presentinvention, wherein a piston is moved to the limit towards a secondchamber side.

FIG. 2 is a sectional view taken on line X—X of FIG. 1.

FIG. 3 is sectional view, like FIG. 1, but wherein the piston is movedto an intermediate position between a first chamber and the secondchamber.

FIG. 4 is a sectional view, like FIG. 1, but wherein the piston is movedto the limit towards the first chamber side.

FIG. 5 is an exploded perspective view of the above-mentioned firstembodiment.

FIG. 6 is a sectional view showing a second embodiment of the presentinvention, wherein an amount adjusting member sits on a valve seat.

FIG. 7 is a sectional view, like FIG. 6, but wherein the amountadjusting member is spaced apart from the valve seat.

FIG. 8 is an exploded perspective view of the above-mentioned secondembodiment.

FIG. 9 is a sectional view showing a third embodiment of the presentinvention, wherein a pressing amount of an amount adjusting member iscomparatively large.

FIG. 10 is a sectional view, like FIG. 9, but wherein a pressing amountof the amount adjusting member is comparatively small.

BEST MODE FOR CARRYING OUT THE INVENTION

Several embodiments of the present invention will be describedhereinafter with reference to FIGS. 1 through 10.

FIGS. 1 through 5, show a first embodiment of the present invention. Arotary damper 1 includes, as chief component elements, a casing 2, arotor 3, a piston 4, a cam member 5 and a coiled spring 6. One of thecasing 2 and the rotor 3 is non-rotatably connected to a device mainbody such as a toilet main body, and the other is non-rotatablyconnected to a rotary body such as a toilet cover.

The casing 2 is of a cylindrical configuration having a bottom portion.The casing 2 includes a cylindrical portion 21 and a bottom portion 22for closing an opening portion at one end of the casing 2. Thecylindrical portion 21 comprises a circular cylindrical portion 21 a onthe opening portion side, and a flat cylindrical portion 21 b on thebottom portion 22 side. The circular cylindrical portion 21 a is of acircular configuration in section. The inside diameter and the outsidediameter of the circular cylindrical portion 21 a are constant. The flatcylindrical portion 21 b is formed in an elongated circularconfiguration whose opposite sides are flat, by being formed in a samesectional configuration as the circular cylindrical portion 21 a andthereafter, press molding opposite side portions, which are 180 degreesaway from each other in the circumferential direction, into two flatportions 21 c, 21 c. The flat cylindrical portion 21 b is non-rotatablyconnected to the device main body or rotary body. The inside of thecylindrical portion 21 is defined as a receiving hole 23. Accordingly,an inner peripheral surface of the receiving hole 23 is of a circularconfiguration in section at an area corresponding to the circularcylindrical portion 21 but it is of an elongated circular configurationin section having a flat surface portion at each of the opposite sides,at an area corresponding to the flat cylindrical portion 21 b. Thebottom portion 22 has a supporting projection 22 a formed at a centralarea thereof and projecting inwards on an axis of the receiving hole 23.

The rotor 3 includes a rotor portion 31 and a connection shaft portion32 whose axes are aligned with each other. The rotor portion 31 isrotatably fitted to an inner periphery of the circular cylindricalportion 21 a of the casing 2 and is prevented from coming off by aretaining ring 11 which is fixedly fitted to the end portion on theopening side of the circular cylindrical portion 21 a. The space betweenthe outer peripheral surface of the rotor portion 31 and the innerperipheral surface of the circular cylindrical portion 21 is sealed witha seal member S such as an O-ring. The connection shaft portion 32 isprojected outside from the casing 2, and two flat surface portions 32 a,32 a are formed on the projected part in such a manner as to be 180degrees away from each other in the circumferential direction. Theconnection shaft portion 32 is non-rotatably connected to the devicemain body or rotary body.

The piston 4 includes a slide portion 41, a lock portion 42 and a camportion 43 which are formed in order from the rotor 3 side towards thebottom portion 22 side. The slide portion 41 has a generally samesectional configuration as the inside of the flat cylindrical portion 21b, and most part of the slide portion 41 on the bottom portion 22 sideis slidingly movably fitted to the flat cylindrical portion 21 b. Owingto this arrangement, the piston 4 is received in the receiving hole 23such that it is unable to rotate but movable in the axial direction. Thelock member 42 is of a plate-like configuration capable of beinginserted into the flat cylindrical portion 21 b. The lock member 42 hasflat surface notch portions 42 a, 42 a which are formed in opposite sideportions facing the direction generally orthogonal to the two flatportions 21 c, 21 c of the, flat cylindrical portion 21 b. Owing to thisarrangement, the lock portion 42 is formed in an elongatedconfiguration, as a whole, whose opposite sides are flat. An annularrecess 44 is formed in the end portion of the lock portion 42 which isin contact with the slide portion 41. The diameter of a bottom portionof the annular recess 44 is smaller than an interval between the flatsurface notch portions 42 a, 42 a. The cam portion 43 is formed in acircular configuration in section. The outside diameter of the camportion 43 is generally same as or slightly smaller than the intervalbetween the flat surface notch portions 43 a, 43 a.

A cam mechanism 7 is disposed between confronting surfaces of the rotorportion 31 of the rotor 3 and the slide portion 41 of the piston 4. Thecam mechanism 7 comprises a pair of cam surfaces 71, 71 formed on theconfronting surface of the rotor 31 with respect to the slide portion41, and a pair of cam surfaces 72, 27 formed on the confronting surfaceof the slide portion 41 with respect to the rotor portion 31. The camsurfaces 71, 72 are in contact with each other. When the rotor 3 isrotated in one direction, the piston 4 is moved from the rotor 3 side tothe bottom portion 22 side. As later described, the movement of thepiston 4 from the bottom portion 22 side to the rotor 3 side isconducted by a second cam mechanism 10.

Because the slide portion 41 of the piston 4 is slidingly movably fittedto the flat cylindrical portion 21 b, the inside of the casing 2 insideof the receiving hole 23 between the bottom portion 22 and the rotor 3is divided into a first chamber R1 on the bottom portion 22 side and asecond chamber R2 on the rotor 3 side. The respective chambers R1, R2are filled with viscous fluid not shown. The first chamber R1 and thesecond chamber R2 are communicated with each other through thecommunication path 8,

That is, on the outer peripheral surface of the slide portion 41 of thepiston 4, two communication grooves 81 extending from one end thereof tothe other end in the axial direction are formed. Accordingly, one endportion (end portion on the rotor 3 side) of each communication groove81 is normally communicated with the second chamber R2 and the other endportion thereof is in communication with the annular recess 44.Moreover, the annular recess 44 is in communication with the firstchamber R1 through a gap formed between the flat surface notch portion42 a formed on the outer peripheral surface of the lock portion 42 andthe inner peripheral surface of the flat cylindrical portion 21 b.Accordingly, the first and second chambers R1, R2 are in communicationwith each other through the gap formed between the flat surface notchportion 42 a and the inner peripheral surface of the flat cylindricalportion 21 b, the annular recess 44 and the communication grooves 81,and the communication path 8 is defined by them. The communication path8 has such a sectional area that the viscous fluid can flow almostwithout any substantial resistance at any place.

The communication path 8 is opened and closed by a stop valve 9. Thestop valve 9 includes a valve body 91. The sectional configuration ofthe inner peripheral surface of the valve body 91 is generally same asthat of the lock portion 42. Accordingly, the cam portion 43 and thelock portion 42 can be inserted into the valve body 91, and when the camportion 43 and the lock member 42 pass through the valve body 91, theinner peripheral surface of the valve body 91 is brought into opposingrelation to the annular recess 44. In that condition, when the valvebody 91 is rotated about 90 degrees with respect to the lock portion 42,the long-axis direction of the valve body 91 and the long-axis directionof the lock portion 42 are generally orthogonal to each other, while theshort-axis direction of the valve body 91 is generally aligned with thelong-axis direction of the lock portion 42. As a result, the lockportion 42 becomes unable to pass through the valve body 91 and thevalve body 91 is prohibited from moving to the bottom portion 22 side bythe lock portion 42.

The sectional configuration of the outer periphery of the valve body 91is generally same as that of the flat cylindrical portion 21 b.Moreover, in a state where the valve body 91 is rotated 90 degrees afterthe lock portion 42 is passed through the valve body 91, the attitude ofthe valve body 91 is same as that of the slide portion 41. Accordingly,the valve body 91 can be inserted into the flat cylindrical portion 21 btogether with the slide portion 41 and fitted into the flat cylindricalportion 21 b such that the valve body 91 is non-rotatable but slidinglymovable. Hence, the valve body 91 maintains its attitude where the body91 is rotated 90 degrees with respect to the lock portion 42 andtherefore, when the valve body 91 is moved to the bottom portion 22side, it unavoidably hits the lock portion 42. This prohibits themovement of the valve body 91 to the bottom portion 22 side.

The thickness of the valve body 91 is smaller than the width of theannular recess 44. Accordingly, the valve body 91 can move in the axialdirection by an amount equal to the difference between the thickness ofthe valve body 91 and the width of the annular recess 44. That is, thevalve body 91 can move between the opposite side surfaces 44 a, 44 b ofthe annular recess 44. When the viscous fluid within the first chamberR1 is going to flow to the second chamber R2 side through thecommunication path 8, the valve body 91 is pushed by the viscous fluidto hit the side surface 44 a on the slide portion 41 side of the annularrecess 44. On the contrary, when the viscous fluid within the secondchamber R2 is going to flow to the first chamber R1 side through thecommunication path 8, the valve body 91 is pushed by the viscous fluidto hit the side surface 44 b on the lock portion 42 side of the annularrecess 44.

The side surface 44 a of the annular recess 44 serves as a valve seat ofthe stop valve 9. When the valve body 91 hits the side surface 44 a, theopening portion at one end of the valve body 91 is blocked with the sidesurface 44 a. Moreover, as previously mentioned, the outer periphery ofthe valve body 91 is same as the sectional configuration of the innerperiphery of the flat cylindrical portion 21 b, and also same as thesectional configuration of the slide portion 41 only excepting thecommunication grooves 81. Accordingly, in a state where the valve body91 hits the side surface 44 a, the end portion of the communication path81 facing the annular recess 44 is blocked with the valve body 91 andthe space between the communication grooves 81 and the annular recess 44is blocked with the valve body 91. By this, the communication path 8 isclosed. That is, the stop valve 9 is closed. As a result, the viscousfluid within the first chamber R1 becomes unable to flow into the secondchamber R2 through the communication path 8.

However, since the piston 4 and the valve body 91 are slidingly moved onthe inner periphery of the flat cylindrical portion 21 b, fine gaps areinevitably formed between the respective outer peripheral surfaces ofthe piston 4 and the valve body 91 and the inner peripheral surface ofthe flat cylindrical portion 21 b. A fine gap is also inevitably formedbetween a connection shaft 52, as later described and a through hole 45,as later described, of the piston 4. When the stop valve 9 is in aclosed position, the viscous fluid within the first chamber R1 is flowedinto the second chamber R2 through the fine gaps. However, the viscousfluid is encountered with a large flowing resistance when it passesthrough the fine gaps. As apparent from this, in the rotary damper 1 ofthis embodiment, fine gaps for intercommunicating the first chamber R1and the second chamber R2 are utilized as a resistance path. It is, ofcourse, accepted that the piston 4 or the valve body 91 is provided witha communication hole, which has an orifice, for intercommunicating thefirst and second chambers R1, R2, and then, this communication hole isused as a resistance path.

On the other hand, when the valve body 91 hits the side surface 44 b ofthe annular recess 44, the communication grooves 81 are in communicationwith the annular recess 44. Moreover, since the dimension of the innerperipheral surface of the valve body 91 in the long-axis direction islarger than the distance between the flat surface notch portions 42 a,42 a of the lock portion 42, a gap is formed between the flat surfacenotch portion 42 a and the inner peripheral surface of the valve body91. Through this gap and through the gap between the flat surface notchportion 42 a and the inner surface of the flat cylindrical portion 21 b,the annular recess 44 is communicated with the first chamber R1.Accordingly, when the valve body 91 hits the side surface 44 b, the stopvalve 9 is brought into an open position to open the communication path8. Hence, the viscous fluid within the second chamber R2 can flow intothe first chamber R1 without any substantial resistance.

The cam member 5 is inserted into the casing 2 at an area on the bottomportion 22 side with its axis aligned with that of the casing 2. One endface of the cam member 5 is in abutment with the bottom portion 22. Thisend face has a supporting hole 51 formed in a central area thereof. Thissupporting hole 51 is for a supporting projection 22 a to be relativelyrotatably fitted therein. The other end face of the cam member 5 has aconnection shaft portion (connection shaft) 52 formed on a central areathereof. This connection shaft portion 52 extends on the axis of thecasing 2. The connection shaft portion 52 is rotatably pierced through athrough hole 45 formed in a central area of the piston 4 and inserted ina connection hole 33 formed in a central area of the rotor 3. A frontend face of the connection shaft portion 52 is in abutment with thebottom surface of the connection hole 33. Accordingly, the rotor 3 andthe cam member 5 are sandwichingly held by the bottom portion 22 and theretaining ring 11. By this, the rotor 3 and the cam member 5 arenon-movable in the axial direction. A plate portion 53 is formed on afront end portion of the connection shaft portion 52. This plate portion53 is non-rotatably inserted in a driving hole portion 34 formed in thebottom surface of the connection hole 33. By this, the cam member 5 isnon-rotatably connected to the rotor 3 so that the cam member 5 rotatesin unison with the rotor 3.

The second cam mechanism 10 is disposed between the confronting surfacesbetween the cam member 5 and the cam portion 43 of the piston 4. Thiscam mechanism 10 comprises a pair of cam surfaces 101, 101 formed onconfronting surfaces of the cam member 5 with respect to the cam portion43, and a pair of cam surfaces 102, 102 formed on confronting surfacesof the cam portion 43 with respect to the cam member 5. The cam surfaces101, 102 are contacted with each other. When the cam member 5 is rotatedin unison with the rotor 3, the second cam mechanism 10 moves the piston4 by the same amount in the same direction as the cam mechanism 7does.That is, at the time the rotor 3 and the cam member 5 are rotated in onedirection, the cam mechanism 7 causes the piston 4 to move from thesecond chamber R2 side to the first chamber R1 side. At that time, thesecond cam mechanism 10 merely allows the piston 4 to move in the samedirection. When the rotor 3 and the cam member 5 are rotated in theother direction, the second cam mechanism 10 causes the piston 4 to movefrom the first chamber R1 side to the second chamber R2 side. At thattime, the cam mechanism 7 merely allows the piston 4 to move in the samedirection.

A coiled spring 6 as biasing means is disposed within the casing 2between the bottom portion 22 and the piston 4. This coiled spring 6 isfor biasing the piston 4 from the first chamber R1 side to the secondchamber R2 side. As previously mentioned, the piston 4 is moved in thesame direction by the cam mechanism 10. Accordingly, the coiled spring6, as an auxiliary member of the second cam mechanism 10, biases thepiston 4 to the second chamber R2 side and is not absolutely necessary.However, since the cam member 5 and the cam portion 43 are small inoutside diameter, the cam surfaces 101, 101 are liable to be worn outquickly when large loads are applied thereto. In order to prevent suchinconveniences, it is preferable to employ the coiled spring 6.

In the rotary damper 1 thus constructed, when the rotor 3 and the cammember 5 are rotated in one direction, the cam mechanism 7 causes thepiston 2 to move from the second chamber R2 side to the first chamber R1side. Then, the viscous fluid within the first chamber R1 is going toflow into the second chamber R2 through the communication path 8.However, the valve body 91 of the stop valve 9 is pushed by the viscousfluid to sits on the side surface 44 a, as a valve seat, of the annularrecess 44. As a result, the stop valve 9 is closed to block thecommunication path 8. Accordingly, the speed of rotation of the rotor 3is restrained to a low speed. At that time, the second cam mechanism 10allows the piston 4 to move in the same direction while maintaining thecontacting relation between the cam surfaces 101, 102.

When the rotor 3 and the cam member 5 are rotated in the otherdirection, the second cam mechanism 10 causes the piston 4 to move fromthe first chamber R1 side to the second chamber R2 side. Then, theviscous fluid within the second chamber R2 is going to flow to the firstchamber R1 side through the communication path 8. The valve body 91 ismoved away from the side surface 44 a by this viscous fluid and the stopvalve 9 is brought into an open position. Accordingly, the viscous fluidwithin the second chamber R2 is flowed into the first chamber R1 throughthe communication path 8 without any substantial resistance. Hence, highspeed rotation of the rotor 3 is allowed.

As apparent from the foregoing description, in the rotary damper 1,since the movement of the piston 4 from the first chamber R1 side to thesecond chamber R2 side is conducted by the second cam mechanism 10, thepiston 4 would not be spaced apart from the rotor 3 even if the rotor 3should be rotated at a high speed in the other direction. In otherwords, the cam surfaces 71, 72 of the cam mechanism 7 are maintained ina normally contacted position. Accordingly, when the rotor 3 is rotatedin one direction immediately after it is rotated in the other direction,the high speed rotation of the rotor 3 is immediately prohibited byresistance of the viscous fluid as soon as the rotor 3 is rotated in onedirection. Hence, in case the rotary damper 1 is disposed between thetoilet main body and the toilet cover, the toilet cover is preventedfrom hitting the toilet main body at a high speed.

Another embodiment of the present invention will now be described. Withrespect to the embodiment to be described hereinafter, only theconstruction different from the above-mentioned embodiment will bedescribed. Those parts, which are same as the first embodiment, aredenoted by same reference numeral and description thereof is omitted.

FIGS. 6 through 8 show a second embodiment of the present invention. Inthe rotary damper 1A of this second embodiment, a vertical hole (firstand second holes) 54 is formed in a cam member 5 such that the verticalholes 54 extends on the axis of the cam member 5. The vertical hole 54extends through the cam member 5. Accordingly, one end portion (left endportion in FIG. 6) of the vertical hole 54 is in communication with afirst chamber R1. A lateral hole 55 is formed in a connection shaftportion 52 of the cam member 5. One end of the lateral hole 55 is openat an inner peripheral surface of the vertical hole 54 and the other endis open an outer peripheral surface of the connection shaft portion 52facing the second chamber R2. Accordingly, the first and the secondchambers R1, R2 are communicated with each other through the verticalhole 54 and the lateral hole 55. A tapered valve seat 56 is formed on anend portion of the vertical hole 54 on the side of the first chamber R1.

An insertion hole 35 is formed in the rotor 3 such that the hole 35extends on the axis of the rotor 3. One end (right end in FIG. 6) of theinsertion hole 35 is open at an outer surface of the rotor 3. The otherend of the insertion hole 35 is open at a bottom surface of the drivinghole 34 and is in communication with the vertical holes 54 through thedriving hole 34 and the communication hole 33. A shaft-like adjustmentmember 12 is slidingly movably inserted into the insertion hole 35. Aspace between an outer peripheral surface of a head portion 12 a of theadjustment member 12 and an inner peripheral surface of the insertionhole 34 is sealed with a seal member 13 such as an O-ring. Accordingly,the viscous fluid is not leaked out between the outer peripheral surfaceof the head portion 12 a and the inner peripheral surface of theinsertion hole 35. The adjustment member 12 has a threaded portion 12 bat an inner area thereof than the head portion 12 a. This threadedportion 12 b is threadingly engaged with the insertion hole 35.Accordingly, by rotationally operating the head portion 12 a of theadjustment member 12 from outside, the adjustment member 12 can beadvanced and retracted in the axial direction of the insertion hole 35.

A portion of the adjustment member 12 located more on the front end sidethan the threaded portion 12 b has a smaller diameter than the insidediameter than the vertical hole 54 and is inserted in the vertical hole54 with a space. A valve portion 12 c is formed on the front end portionof the adjustment member 12. When the head portion 12 a of theadjustment member 12 is moved to a predetermined position towards theinner side of the insertion hole 35, the valve portion 12 c sits on thevalve seat 56. When the valve portion 12 c sits on the valve seat 56, aspace between the portion of the vertical hole 54 on the first chamberR1 side and the portion of the vertical hole 54 on the second chamber R2side is blocked with the valve portion 12 c. Accordingly, the viscousfluid does not flow through the vertical holes 54 nor the lateral hole55. On the other hand, when the valve portion 12 c is brought away fromthe valve seat 56 towards the second chamber 2R side, the viscous fluidwithin the first chamber R1 flows into the second chamber R2 through thevertical hole 54 and the lateral hole 55. At that time, the viscousfluid is encountered with an amount of flowing resistance which amountcorresponds to an interval between the valve seat 56 and the valveportion 12 c. The speed of rotation of the rotor 3 in one direction isrestricted by the flowing resistance against the viscous fluid.Accordingly, the speed of rotation of the rotor 3 in one direction canbe adjusted by adjusting the interval between the valve seat 56 and thevalve portion 12 c.

As apparent from the foregoing description, a resistance path is formedby the vertical hole 54, the lateral hole 55, the valve seat 56 and thevalve portion 12 c. Since the viscous fluid within the second chamber R2flows into the first chamber R1 through the communication path 8, it isnot encountered with a large flowing resistance even when the valveportion 12 c sits on the valve seat 56.

In the rotary damper 1A thus constructed, when the rotor 3 is rotated inone direction to cause the piston 4 to move from the second chamber R2side to the first chamber R1 side, the viscous fluid within the firstchamber R1 is going to flow into the second chamber R2 through thevertical hole 54 and the lateral hole 55, as the resistance path. Atthat time, if the valve portion 12 c sits on the valve seat 56, thevertical hole 54 is blocked with the valve portion 12 c and therefore,the viscous fluid within the first chamber R1 cannot pass the verticalhole 54. Accordingly, the viscous fluid within the first chamber R1flows into the second chamber R2 through the gaps inevitably formed inthe respective parts between the first chamber R1 and the second chamberR2 as in the above-mentioned first embodiment. Hence, the viscous fluidis encountered with a large flowing resistance. The high speed rotationof the rotor 3 is prohibited by this. On the other hand, when the valveportion 12 c is spaced apart from the valve seat 56 towards the secondchamber R2 side, the viscous fluid within the first chamber R1 passesthrough the interval between the valve seat 56 and the valve seat 12 cand flows into the second chamber R2 through the vertical hole 54 andthe lateral hole 55, Accordingly, in that case, the flowing resistancereceived by the viscous fluid is reduced by an amount equal to theviscous fluid in the first chamber R1 which flows passing through thevertical hole 54 and the lateral hole 55, and the rotor 3 can rotate ata high speed to that extent. The speed of rotation of the rotor 3 can beadjusted by adjusting the interval between the valve seat 56 and thevalve portion 12 c.

In case the rotor 3 is rotated in the other direction and the piston 4is moved from the first chamber R1 side to the second chamber R2 side,the viscous fluid within the second chamber R2 flows into the firstchamber R1 through the communication path 8 as in the above-mentionedfirst embodiment. Of course, when the valve portion 12 c is spaced apartfrom the valve seat 56, a part of the viscous fluid within the secondchamber R2 flows into the first chamber R1 through the lateral hole 55and the vertical hole 54. Accordingly, the rotor 3 can rotate at ahigher speed.

FIGS. 9 and 10 show a third embodiment of the present invention. In arotary damper 1B of this third embodiment, instead of the valve seat 56of the second embodiment, a reduced-diameter hole portion 57 is formedin an inner peripheral surface of a vertical hole 54. A front endportion of an amount adjusting member 14 is slidingly movably fitted tothis reduced-diameter hole portion 57. The amount adjusting member 14 isformed in the same manner as the adjustment member 12 only exceptingthat the valve portion 12 c is not formed. A head portion 14 a is sealedwith an inner peripheral surface of an insertion hole 35 through a sealmember 13, and a threaded portion 14 b is threadingly engaged with theinsertion hole 35.

In the rotary damper 1B of this third embodiment, by removing the amountadjusting member 14, the viscous fluid can be introduced into a firstchamber R1 through the insertion hole 35 and a vertical hole 54 and theviscous fluid can also be introduced from the first chamber R1 to thesecond chamber R2. An inlet path is formed by the insertion hole 35 andthe vertical hole 54. Error tends to occur to the amounts of viscousfluid introduced into the first and second chambers R1, R2 depending oneach rotary damper. Such error can be compensated by an amount ofinsertion of the amount adjusting member 14 into the reduced-diameterhole portion 57. That is, in case the filling amounts of viscous fluidinto the first and second chambers R1, R2 are small, it suffices thatthe amount of insertion of the amount adjusting member 14 into thereduced-diameter hole portion 57 is increased as shown in FIG. 9. Incase the filling amounts of viscous fluid is large, it suffices that theamount of insertion of the amount adjusting member 14 into thereduced-diameter hole portion 57 is decreased as shown in FIG. 10.

It should be noted that the present invention is not limited to theabove-mentioned embodiments but that many changes and modifications canbe made in accordance with necessity.

For example, in the above embodiments, although the first and secondchambers R1, R2 are communicated with each other through thecommunication path 8 and the communication path 8 is opened and closedby the stop valve 9, the first and second chambers R1, R2 may becommunicated with each other only through the resistance path withoutemploying the communication path 8 and the stop valve 9. In that case,the high speed rotation is prohibited irrespective of the direction ofrotation of the rotor. Especially, when no communication path 8 isemployed in the second embodiment where the resistance path is formed bythe vertical hole 54, the lateral hole 55, the valve seat 56 and thevalve portion 12 c, the speed of rotation of the rotor 3 can be adjustedby adjusting the interval between the valve seat 56 and the valveportion 12 c, irrespective of the direction of rotation of the rotor 3.

Moreover, in the above embodiments, the connection shaft portion 52 isdisposed on the cam member 5, this connection shaft portion 52 ispierced through the piston 4 and non-rotatably connected to the rotor 3.It is also accepted that the connection shaft portion is disposed on therotor 3, and the connection shaft portion 52 is pierced through thepiston 4 and non-rotatably connected to the cam member 5. It is also aninteresting alternative that the connecting shaft portion 52 is formedseparately from the cam member 5 and the rotor 3, and opposite endportions of the connecting shaft portion 52 are non-rotatably connectedto the cam member 5 and the rotor 3.

Moreover, in the above embodiments, although the cam mechanism 7 isformed by the cam surface 71 formed on the rotor 3 and the cam surface72 formed on the piston 4, it is also accepted that a cam surface isformed on one of the rotor 3 and the piston 4, and a projection to beabutted with the cam surface is formed on the other. The same can beapplicable to the second cam mechanism 10.

INDUSTRIAL APPLICABILITY

A rotary damper according to the present invention is useful as a rotarydamper which is disposed between a device main body and a rotary bodyrotatably supported thereon, such as a toilet main body and a toiletcover and which is adapted to prevent high speed rotation of the rotarybody at least in one direction so that the rotary body can rotate at alow speed. It is especially suited to be used for surely prohibitinghigh-speed rotation of the rotary body in one direction.

We claim:
 1. A rotary damper including a casing (2) having a receivinghole (23), a rotor fitted to said receiving hole (23) such that saidrotor is non-movable in an axial direction thereof but rotatable, apiston (4) inserted into said receiving hole (23) between said rotor (3)and a bottom portion (22) of said receiving hole (23) such that saidpiston (4) is movable in the axial direction thereof but non-rotatable,and for defining the inside of said receiving hole (23) into a firstchamber (R1) on said bottom portion (22) side and a second chamber (R2)on said rotor (3) side, and viscous fluid filled in said first andsecond chambers (R1, R2), a cam mechanism (7) for allowing movement ofsaid piston (4) from said second chamber (R2) side to said first chamber(R1) side when said rotor (3) is rotated in one direction and forallowing movement from said first chamber (R1) side to said secondchamber (R2) side when said rotor (3) is rotated in the other directionbeing disposed between said rotor (3) and said piston (4), wherein a cammember (5) is disposed within said first chamber (R1) such that said cammember (5) is non-movable in the axial direction of said receiving hole(23) but rotatable, said cam member (5) is non-rotatably connected tosaid rotor (3), a second cam mechanism (10) for allowing movement ofsaid piston (4) from said second chamber (R2) side to said first chamber(R1) side by said cam mechanism (7) when said rotor (3) is rotated inone direction and for allowing movement of said piston (4) from saidfirst chamber (R1) side to said second chamber (R2) side when said rotor(3) is rotated in the other direction is disposed between said rotor (3)and said piston (4), and amounts of movement of said piston (4)corresponding to rotation of said rotor (3) by said second cam mechanism(10) and said cam mechanism (7) are set to be equal.
 2. A rotary damperaccording to claim 1, wherein there are provided a communication path(8) for flowing the viscous fluid without any resistance and aresistance path for flowing the viscous fluid with a predetermined valueof resistance, between said first chamber (R1) and said second chamber(R2), and a stop valve (9) for opening said communication path (8) whenthe viscous fluid flows in one direction within said communication path(8) and for closing said communication path (8) when the viscous fluidflows in the other direction within said communication path (8) isdisposed at said communication path (8).
 3. A rotary damper according toclaim 2, wherein an adjustment member (12) for adjusting a flow patharea of said resistance path is disposed at said resistance path suchthat said adjustment member (12) can be operated from outside.
 4. Arotary damper according to claim 3, wherein said piston (4) has athrough hole (45) formed in a central area thereof and extendingtherethrough in an axial direction thereof, and said rotor (3) and saidcam member (4) are non-rotatably connected to each other through aconnection shaft (52) rotatably inserted into said through hole (45). 5.A rotary damper according to claim 4, wherein said resistance pathincludes a first hole (54) extending through a central area of said cammember (5) in an axial direction thereof, a second hole (54) extendingthrough a central area of said connection shaft (52) in an axialdirection thereof, and a lateral hole (55) extending from said secondhole (54) to an outer peripheral surface of said connection shaft (52)facing said second chamber (R2), an insertion hole (35) is formed in acentral area of said rotor (3) in such a manner as to extendtherethrough in an axial direction thereof, and said adjustment member(12) is inserted at least into said second hole (54) from an externalopening portion of said insertion hole (35).
 6. A rotary damperaccording to claim 2, which further comprises inlet paths (34, 54)communicating with said first chamber (R1) or said second chamber (R2)from outside, and wherein said inlet paths (35, 54) are provided, in theform of a seal, with an amount adjusting member (14), whose insertionamount into said inlet paths (35, 54) can be operated from outside.
 7. Arotary damper according to claim 6, wherein said piston (4) has athrough hole (45) formed in a central area thereof and extendingtherethrough in an axial direction thereof, and said rotor (3) and saidcam member (4) are non-rotatably connected to each other through aconnection shaft (52) rotatably inserted into said through hole (45). 8.A rotary damper according to claim 7, wherein said inlet paths (35, 54)includes a first hole (54) extending through a central area of said cammember (5) in an axial direction thereof, a second hole (54) extendingthrough a central area of said connection shaft (52) in an axialdirection thereof, and an insertion hole (35) extending through acentral area of said rotor (3) in an axial direction thereof, and saidamount adjusting member (14) is inserted into said inlet path from anexternal opening portion of said insertion hole (35).
 9. A rotary damperaccording to claim 2, wherein said piston (4) has a through hole (45)formed in a central area thereof and extending in an axial directionthereof, and said rotor (3) and said cam member (4) are non-rotatablyconnected to each other through a connection shaft (52) rotatablyinserted into said through hole (45).
 10. A rotary damper according toclaim 1, wherein said piston (4) has a through hole (45) formed in acentral area thereof and extending in an axial direction thereof, andsaid rotor (3) and said cam member (4) are non-rotatably connected toeach other through a connection shaft (52) rotatably inserted into saidthrough hole (45).